Blank pushbuttons used for auxiliary features

I've read on here that the blank black pushbuttons on the center console and between Sport/DSC OFF that these are reserved for Euro features not available in North America.

I want to use them for some auxiliary features. The one on the console next to the Rear Defog (by the driver's knee) would be perfect for a momentary switch to activate my garage door opener. Anyone do something like this? I figure I could find some kind of momentary switch that could be wired to the guts of a handheld remote for my door opener, and I could cut down the length of the blank cover enough to activate the switch.

I want to do the same for the middle button between Sport and DSC OFF to add a different feature with , but I've read there might be a circuit board there.